The present invention generally relates to systems and methods for detecting problems that occur when encoding uncompressed video or transcoding compressed video.
In the video industry, typically video is recorded in an uncompressed format. If video is stored as a compressed format, it is usually first uncompressed before being compressed again to another codec (transcoding). The uncompressed format is typically compressed and encoded for storage, e.g., a DVD, or for transmission, e.g., from a cable headend.
FIG. 1 illustrates a prior art video processing system 100. As illustrated, video processing system 100 includes an analog tuner 102, a digital tuner 104, a decoder 106, an OR gate 108, a frame buffer 110, a video analyzer 114, a user interface 116 and an encoder 112. An area 138 above a dotted line 136 represents the portions of video processing system 100 dealing with uncompressed video. An area 140 below dotted line 136 represents the portions of video processing system 100 dealing with compressed video.
Analog tuner 102 is arranged to receive an analog signal 118 and output a tuned signal 120. Digital tuner 104 is arranged to receive a digital signal 122 and output a tuned signal 124. Decoder 106 receives tuned signal 124 and outputs a digital decoded signal 126. OR gate 108 is arranged to receive data corresponding to image frames in tuned signal 120 and decoded signal 126, and output a data signal 128.
Data corresponding to image frames in signal 128 are stored in frame buffer 110 which outputs a signal 130. Video analyzer 114 receives signal 130 and output a processed signal 132. User interface 116 is arranged to receive processed signal 132. Encoder 112 is arranged to receive signal 130 and output a signal 134.
In operation video processing system 100 receives video in analog or digital format, where video comprises a sequence of image frames. Image frames are comprised of matrices of pixels, each pixel being represented by data corresponding to luminance and color information, the data of all the pixels making up the data of one image frame, the data of all the image frames making up the data of the video stream.
Some prior art video processing systems may have only one of an analog tuner and a digital tuner. Because video processing system 100 includes analog tuner 102 and digital tuner 104, it may process video from either tuner. OR gate 108 enables a video stream to be processed by passing either tuned signal 120 or decoded signal 126 as data signal 128. Data corresponding to image frames in signal 128 are stored in frame buffer 110, which may then be subsequently output as signal 130 to encoder 112. Encoder 112 then encodes the data in signal 130 by known methods and outputs signal 134 for storage, e.g., on a digital video disk (DVD), or delivery to the customers, e.g., satellite television. The data in signal 130 additionally passes to video analyzer 114. Video analyzer 114 analyzes the data corresponding to image frames and may determine whether there is a problem with the video. Upon detection of a problem, video analyzer 114 provides an indication of a problem to a user by way of user interface 116.
A more detailed discussion of video analyzer 114 will now be provided. Video analyzer 114 detects system problems as evidences by a plurality of black images, i.e., a black portion of the video, or unwanted repeated images, i.e., a frozen portion of the video. After detecting a problem, the system may signal a user of a problem with the video. The detection is done by observing sequence of image frames and the luminance and chromatic information of a subset of the total number of pixels of the image frame.
Signal 134 includes a stream of video data corresponding to a plurality of image frames. However, if a portion of the video freezes or turns black, signal 134 will include a portion of the video data corresponding to the frozen image frames or the black image frames.
Storing or transmitting frozen or black image frames is not desired. Accordingly, video analyzer 114 monitors the stream of video data and provides a signal when signal 134 includes a portion of video data corresponding to frozen image frames or black image frames.
One prior art video analyzer detects black/freeze portions of a video by using horizontal motion detector to detect motion across the horizontal axis of the image frames within the video and by using a similar vertical motion detector to detect motion across the vertical axis of the image frames within the video. A problem with this prior art video analyzer is that it is hardware based and its computational method is complex and is not flexible.
Another prior art video analyzer detects the freeze through pixel by pixel comparison of entire image frames, and then averages out the observations over several image frames. A problem with this prior art video analyzer is that it is extremely computationally intensive.
The prior art systems discussed above do not address the presence of noise, i.e., snow, which is often found in video coming from analog domain. Furthermore, the hardware and computational complexity with prior art video analyzers are rigidly fixed and are not scalable.
What is needed is a system and method that is able to detect black/snow or freeze in a video stream with less hardware and less computational complexity, and is scalable and reduces the effect of noise in the system.